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<title>Managed Beans - The Java EE 6 Tutorial</title>
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      <td width="400px"><p class="toc level1"><a href="docinfo.html">Document Information</a></p>
<p class="toc level1 tocsp"><a href="gexaf.html">Preface</a></p>
<p class="toc level1 tocsp"><a href="gfirp.html">Part&nbsp;I&nbsp;Introduction</a></p>
<p class="toc level2"><a href="bnaaw.html">1.&nbsp;&nbsp;Overview</a></p>
<p class="toc level2"><a href="gfiud.html">2.&nbsp;&nbsp;Using the Tutorial Examples</a></p>
<p class="toc level1 tocsp"><a href="bnadp.html">Part&nbsp;II&nbsp;The Web Tier</a></p>
<p class="toc level2"><a href="bnadr.html">3.&nbsp;&nbsp;Getting Started with Web Applications</a></p>
<p class="toc level2"><a href="bnaph.html">4.&nbsp;&nbsp;JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="giepx.html">5.&nbsp;&nbsp;Introduction to Facelets</a></p>
<p class="toc level2"><a href="gjddd.html">6.&nbsp;&nbsp;Expression Language</a></p>
<p class="toc level2"><a href="bnaqz.html">7.&nbsp;&nbsp;Using JavaServer Faces Technology in Web Pages</a></p>
<p class="toc level2"><a href="gjcut.html">8.&nbsp;&nbsp;Using Converters, Listeners, and Validators</a></p>
<p class="toc level2"><a href="bnatx.html">9.&nbsp;&nbsp;Developing with JavaServer Faces Technology</a></p>
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<p class="toc level3"><a href="">Managed Beans</a></p>
<p class="toc level4"><a href="#bnaqn">Creating a Managed Bean</a></p>
<p class="toc level4"><a href="#bnaqp">Using the EL to Reference Managed Beans</a></p>
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<p class="toc level3 tocsp"><a href="bnaty.html">Writing Bean Properties</a></p>
<p class="toc level4"><a href="bnaty.html#bnatz">Writing Properties Bound to Component Values</a></p>
<p class="toc level5"><a href="bnaty.html#bnaub"><tt>UIInput</tt> and <tt>UIOutput</tt> Properties</a></p>
<p class="toc level5"><a href="bnaty.html#bnauc"><tt>UIData</tt> Properties</a></p>
<p class="toc level5"><a href="bnaty.html#bnaud"><tt>UISelectBoolean</tt> Properties</a></p>
<p class="toc level5"><a href="bnaty.html#bnaue"><tt>UISelectMany</tt> Properties</a></p>
<p class="toc level5"><a href="bnaty.html#bnauf"><tt>UISelectOne</tt> Properties</a></p>
<p class="toc level5"><a href="bnaty.html#bnaug"><tt>UISelectItem</tt> Properties</a></p>
<p class="toc level5"><a href="bnaty.html#bnauh"><tt>UISelectItems</tt> Properties</a></p>
<p class="toc level4 tocsp"><a href="bnaty.html#bnauk">Writing Properties Bound to Component Instances</a></p>
<p class="toc level4"><a href="bnaty.html#bnaul">Writing Properties Bound to Converters, Listeners, or Validators</a></p>
<p class="toc level3 tocsp"><a href="bnavb.html">Writing Managed Bean Methods</a></p>
<p class="toc level4"><a href="bnavb.html#bnavc">Writing a Method to Handle Navigation</a></p>
<p class="toc level4"><a href="bnavb.html#bnavd">Writing a Method to Handle an Action Event</a></p>
<p class="toc level4"><a href="bnavb.html#bnave">Writing a Method to Perform Validation</a></p>
<p class="toc level4"><a href="bnavb.html#bnavf">Writing a Method to Handle a Value-Change Event</a></p>
<p class="toc level3 tocsp"><a href="gircz.html">Using Bean Validation</a></p>
<p class="toc level4"><a href="gircz.html#gkcrg">Validating Null and Empty Strings</a></p>
<p class="toc level2 tocsp"><a href="gkmaa.html">10.&nbsp;&nbsp;JavaServer Faces Technology Advanced Concepts</a></p>
<p class="toc level2"><a href="bnawo.html">11.&nbsp;&nbsp;Configuring JavaServer Faces Applications</a></p>
<p class="toc level2"><a href="gkiow.html">12.&nbsp;&nbsp;Using Ajax with JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="gkhxa.html">13.&nbsp;&nbsp;Advanced Composite Components</a></p>
<p class="toc level2"><a href="bnavg.html">14.&nbsp;&nbsp;Creating Custom UI Components</a></p>
<p class="toc level2"><a href="bnafd.html">15.&nbsp;&nbsp;Java Servlet Technology</a></p>
<p class="toc level2"><a href="bnaxu.html">16.&nbsp;&nbsp;Internationalizing and Localizing Web Applications</a></p>
<p class="toc level1 tocsp"><a href="bnayk.html">Part&nbsp;III&nbsp;Web Services</a></p>
<p class="toc level2"><a href="gijti.html">17.&nbsp;&nbsp;Introduction to Web Services</a></p>
<p class="toc level2"><a href="bnayl.html">18.&nbsp;&nbsp;Building Web Services with JAX-WS</a></p>
<p class="toc level2"><a href="giepu.html">19.&nbsp;&nbsp;Building RESTful Web Services with JAX-RS</a></p>
<p class="toc level2"><a href="gjjxe.html">20.&nbsp;&nbsp;Advanced JAX-RS Features</a></p>
<p class="toc level2"><a href="gkojl.html">21.&nbsp;&nbsp;Running the Advanced JAX-RS Example Application</a></p>
<p class="toc level1 tocsp"><a href="bnblr.html">Part&nbsp;IV&nbsp;Enterprise Beans</a></p>
<p class="toc level2"><a href="gijsz.html">22.&nbsp;&nbsp;Enterprise Beans</a></p>
<p class="toc level2"><a href="gijre.html">23.&nbsp;&nbsp;Getting Started with Enterprise Beans</a></p>
<p class="toc level2"><a href="gijrb.html">24.&nbsp;&nbsp;Running the Enterprise Bean Examples</a></p>
<p class="toc level2"><a href="bnbpk.html">25.&nbsp;&nbsp;A Message-Driven Bean Example</a></p>
<p class="toc level2"><a href="gkcqz.html">26.&nbsp;&nbsp;Using the Embedded Enterprise Bean Container</a></p>
<p class="toc level2"><a href="gkidz.html">27.&nbsp;&nbsp;Using Asynchronous Method Invocation in Session Beans</a></p>
<p class="toc level1 tocsp"><a href="gjbnr.html">Part&nbsp;V&nbsp;Contexts and Dependency Injection for the Java EE Platform</a></p>
<p class="toc level2"><a href="giwhb.html">28.&nbsp;&nbsp;Introduction to Contexts and Dependency Injection for the Java EE Platform</a></p>
<p class="toc level2"><a href="gjbls.html">29.&nbsp;&nbsp;Running the Basic Contexts and Dependency Injection Examples</a></p>
<p class="toc level2"><a href="gjehi.html">30.&nbsp;&nbsp;Contexts and Dependency Injection for the Java EE Platform: Advanced Topics</a></p>
<p class="toc level2"><a href="gkhre.html">31.&nbsp;&nbsp;Running the Advanced Contexts and Dependency Injection Examples</a></p>
<p class="toc level1 tocsp"><a href="bnbpy.html">Part&nbsp;VI&nbsp;Persistence</a></p>
<p class="toc level2"><a href="bnbpz.html">32.&nbsp;&nbsp;Introduction to the Java Persistence API</a></p>
<p class="toc level2"><a href="gijst.html">33.&nbsp;&nbsp;Running the Persistence Examples</a></p>
<p class="toc level2"><a href="bnbtg.html">34.&nbsp;&nbsp;The Java Persistence Query Language</a></p>
<p class="toc level2"><a href="gjitv.html">35.&nbsp;&nbsp;Using the Criteria API to Create Queries</a></p>
<p class="toc level2"><a href="gkjiq.html">36.&nbsp;&nbsp;Creating and Using String-Based Criteria Queries</a></p>
<p class="toc level2"><a href="gkjjf.html">37.&nbsp;&nbsp;Controlling Concurrent Access to Entity Data with Locking</a></p>
<p class="toc level2"><a href="gkjia.html">38.&nbsp;&nbsp;Improving the Performance of Java Persistence API Applications By Setting a Second-Level Cache</a></p>
<p class="toc level1 tocsp"><a href="gijrp.html">Part&nbsp;VII&nbsp;Security</a></p>
<p class="toc level2"><a href="bnbwj.html">39.&nbsp;&nbsp;Introduction to Security in the Java EE Platform</a></p>
<p class="toc level2"><a href="bncas.html">40.&nbsp;&nbsp;Getting Started Securing Web Applications</a></p>
<p class="toc level2"><a href="bnbyk.html">41.&nbsp;&nbsp;Getting Started Securing Enterprise Applications</a></p>
<p class="toc level1 tocsp"><a href="gijue.html">Part&nbsp;VIII&nbsp;Java EE Supporting Technologies</a></p>
<p class="toc level2"><a href="gijto.html">42.&nbsp;&nbsp;Introduction to Java EE Supporting Technologies</a></p>
<p class="toc level2"><a href="bncih.html">43.&nbsp;&nbsp;Transactions</a></p>
<p class="toc level2"><a href="bncjh.html">44.&nbsp;&nbsp;Resource Connections</a></p>
<p class="toc level2"><a href="bncdq.html">45.&nbsp;&nbsp;Java Message Service Concepts</a></p>
<p class="toc level2"><a href="bncgv.html">46.&nbsp;&nbsp;Java Message Service Examples</a></p>
<p class="toc level2"><a href="gkahp.html">47.&nbsp;&nbsp;Advanced Bean Validation Concepts and Examples</a></p>
<p class="toc level2"><a href="gkeed.html">48.&nbsp;&nbsp;Using Java EE Interceptors</a></p>
<p class="toc level1 tocsp"><a href="gkgjw.html">Part&nbsp;IX&nbsp;Case Studies</a></p>
<p class="toc level2"><a href="gkaee.html">49.&nbsp;&nbsp;Duke's Tutoring Case Study Example</a></p>
<p class="toc level1 tocsp"><a href="idx-1.html">Index</a></p>
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<a name="bnaqm"></a><h2>Managed Beans</h2>
<a name="indexterm-535"></a><a name="indexterm-536"></a><p>A typical JavaServer Faces application includes one or more managed beans, each of
which can be associated with the components used in a particular page. This
section introduces the basic concepts of creating, configuring, and using managed beans in
an application.</p>



<a name="bnaqn"></a><h3>Creating a Managed Bean</h3>
<a name="indexterm-537"></a><a name="indexterm-538"></a><p>A managed bean is created with a constructor with no arguments, a
set of properties, and a set of methods that perform functions for a
component. Each of the managed bean properties can be bound to one of
the following:</p>


<ul><li><p>A component value</p>

</li>
<li><p>A component instance</p>

</li>
<li><p>A converter instance</p>

</li>
<li><p>A listener instance</p>

</li>
<li><p>A validator instance</p>

</li></ul>
<p>The most common functions that managed bean methods perform include the following:</p>


<ul><li><p>Validating a component&rsquo;s data</p>

</li>
<li><p>Handling an event fired by a component</p>

</li>
<li><p>Performing processing to determine the next page to which the application must navigate</p>

</li></ul>
<p>As with all JavaBeans components, a property consists of a private data field
and a set of accessor methods, as shown by this code:</p>

<pre>Integer userNumber = null;
...
public void setUserNumber(Integer user_number) {
    userNumber = user_number;
}
public Integer getUserNumber() {
    return userNumber;
}
public String getResponse() {
    ...
}</pre><p>When bound to a component&rsquo;s value, a bean property can be any of
the basic primitive and numeric types or any Java object type for
which the application has access to an appropriate converter. For example, a property can
be of type <tt>Date</tt> if the application has access to a converter that
can convert the <tt>Date</tt> type to a <tt>String</tt> and back again. See
<a href="bnaty.html">Writing Bean Properties</a> for information on which types are accepted by which component tags.</p>

<p>When a bean property is bound to a component instance, the property&rsquo;s type
must be the same as the component object. For example, if a
<tt>javax.faces.component.UISelectBoolean</tt> component is bound to the property, the property must accept and return
a <tt>UISelectBoolean</tt> object. Likewise, if the property is bound to a converter, validator,
or listener instance, the property must be of the appropriate converter, validator, or
listener type.</p>

<p>For more information on writing beans and their properties, see <a href="bnaty.html">Writing Bean Properties</a>.</p>



<a name="bnaqp"></a><h3>Using the EL to Reference Managed Beans</h3>
<a name="indexterm-539"></a><p>To bind  component values and objects to managed bean properties or to
reference managed bean methods from  component tags, page authors use the Expression
Language syntax. As explained in <a href="bnahq.html">Overview of the EL</a>, the following are some of the
features that EL offers:</p>


<ul><li><p>Deferred evaluation of expressions</p>

</li>
<li><p>The ability to use a value expression to both read and write data</p>

</li>
<li><p>Method expressions</p>

</li></ul>
<p>Deferred evaluation of expressions is important because the JavaServer Faces lifecycle is split
into several phases in which component event handling, data conversion and validation, and
data propagation to external objects are all performed in an orderly fashion. The
implementation must be able to delay the evaluation of expressions until the proper
phase of the lifecycle has been reached. Therefore, the implementation&rsquo;s tag attributes always use
deferred-evaluation syntax, which is distinguished by the <tt>#{}</tt> delimiter.</p>

<p><a name="indexterm-540"></a>To store data in external objects, almost all JavaServer Faces tag attributes use
lvalue expressions, which are expressions that allow both getting and setting data on
external objects.</p>

<p>Finally, some component tag attributes accept method expressions that reference methods that handle
component events or validate or convert component data.</p>

<p>To illustrate a JavaServer Faces tag using the EL, suppose that a
tag of an application referenced a method to perform the validation of user
input:</p>

<pre>&lt;h:inputText id="userNo"
     value="#{UserNumberBean.userNumber}"
     validator="#{UserNumberBean.validate}" /></pre><p>This tag binds the <tt>userNo</tt> component&rsquo;s value to the <tt>UserNumberBean.userNumber</tt> managed bean property by
using an lvalue expression. The tag uses a method expression to refer
to the <tt>UserNumberBean.validate</tt> method, which performs validation of the component&rsquo;s local value. The local
value is whatever the user enters into the field corresponding to this tag.
This method is invoked when the expression is evaluated.</p>

<p><a name="indexterm-541"></a>Nearly all JavaServer Faces tag attributes accept value expressions. In addition to referencing bean
properties, value expressions can reference lists, maps, arrays, implicit objects, and resource bundles.</p>

<p><a name="indexterm-542"></a><a name="indexterm-543"></a><a name="indexterm-544"></a><a name="indexterm-545"></a>Another use of value expressions is binding a component instance to a managed
bean property. A page author does this by referencing the property from the
<tt>binding</tt> attribute:</p>

<pre>&lt;inputText binding="#{UserNumberBean.userNoComponent}" /></pre><p><a name="indexterm-546"></a>In addition to using expressions with the standard component tags, you can configure
your custom component properties to accept expressions by creating <tt>javax.el.ValueExpression</tt> or <tt>javax.el.MethodExpression</tt> instances
for them. </p>

<p>For information on the EL, see <a href="gjddd.html">Chapter&nbsp;6, Expression Language</a>.</p>

<p>For information on referencing managed bean methods from component tags, see <a href="bnatn.html">Referencing a Managed Bean Method</a>.</p>


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